32 
Colorado Experiment Station 
trates in the First Foot and the Succeeding Three Feet of Soil in 
1913 and 1915” shows plainly that the total amount in the top fouy 
feet of soil was not less in 1915 than in 1913, but it also shows that 
the distribution was quite different in the two years. This, however, 
should make but little difference, for reference to the tables giving 
the nitric nitrogen in the soil samples taken throughout the season 
to a depth of four feet, show that the fourth foot does not usually, 
even in 1915, when our soil was kept moist by a succession of mod¬ 
erate rains, contain any large quantity of nitric nitrogen. We con¬ 
sider this depth the limit of the feeding area of the wheat plant. 
But if this should be too great a depth to take under our conditions, 
and if the plants do not feed to a greater depth than three feet, 
this would not alter the statement made relative to the total supply 
of nitric nitrogen in the two years. Further, any question concern¬ 
ing the relative supply of nitric nitrogen which might apply to the 
check plots in the respective years, could scarcely apply to the plots 
to which we applied 120 pounds of nitric nitrogen per acre in three 
applications, made at intervals of approximately four weeks, with 
the purpose of maintaining an excessive supply of this form of nitro¬ 
gen in the soil. The first application of 40 pounds of nitrogen per 
acre was harrowed in to a depth of from two to three inches. We 
had to depend upon the rain and irrigating water for the distribu¬ 
tion of the succeeding applications. We made no attempt to follow 
the distribution of these 120 pounds of nitrogen through the soil. 
It might have been interesting if we had been able to do so and fur¬ 
ther to have determined what portion of it was utilized by the plant 
and how much of it was lost in the soil. We have, in our observations 
of the effects produced upon the plants, a basis for a very rough esti¬ 
mate of the relative effects of the quantities, 40, 80 and 120 pounds, 
applied to the different plots. This rough judgment is that 80 
pounds, applied in two portions of 40 pounds each, produces on our 
soil, almost, if not altogether, as great effects as 120 pounds ap¬ 
plied in three portions of 40 pounds each. The effects of 40 pounds, 
applied at the time of planting, produce quite as deep a color in 
the growing plants, and the limits of the area to which it has been 
applied are quite as definitely marked as those of 80 or 120 pounds. 
This statement does not hold in other respects, for we shall see that 
the effects of the larger applications are quite regularly bigger 
than those of the smaller applications. It does not seem probable 
that either the quantity of nitric nitrogen present in the two years, 
or the distribution of the same in the soil, varied enough to produce 
the differences in the nitrogen content of the plants which we ac¬ 
tually find. The stems constitute approximately 65 percent of the 
total plant, and while the amount of nitrogen present is smaller than 
